Conveying systems are often employed to convey articles through a series of working stations. In certain conveyor systems, it is desired to form a stack of articles from a single transferred row of articles and transfer the assembled stack to packaging or other working equipment. Frequently, a variety of article sizes are conveyed in an intermingled order and the conveying system is operable to separate the articles based on the type and/or size of article before the stack is formed. A series of stacking units are often utilized and the stacking units must be capable of automatically separating and stacking the dissimilar articles and feeding the stacks onto a discharge conveyor without interference between stacks.
The present invention is directed to a method and apparatus for stacking individual articles and feeding the assembled stack to a discharge conveyor. A plurality of articles, such as video cassette containers, compact disc containers, or the like, are conveyed on an infeed conveyor in an upright singulated fashion. A stacker mechanism receives each of the individual articles on a transfer platform located at a transfer location. Upon receiving one of the articles, an article pusher assembly is activated to push the article off of the transfer platform and onto a support platform. The support platform is used to assemble the stack from the plurality of individual articles fed successively from the transfer location.
The outermost article of the stack is pushed into contact with a backstop contained within a back-up slide assembly. The backstop is connected to a single-acting back-up cylinder that is unpressurized, such that the backstop is free to move along the support platform as the stack is assembled. A friction device contained in the back-up slide assembly provides the required force to support the outermost article of the stack.
A hold-back member is positioned between the transfer location and the support platform such that after an article is added to the stack, the hold-back member is moved to an extended, retaining position, during which the hold-back member supports the innermost article of the stack. Thus, the combination of the hold-back member and the backstop supports the stack at both the inner and outer ends of the stack.
Once a complete stack of articles is assembled on the support platform, a stack pusher assembly is activated to push the stack off of the support platform and onto a discharge or outfeed conveyor assembly. Specifically, the stack pusher assembly includes a pusher plate that is attached to a drive cylinder and is movable between a retracted position and an extended position.
Once a complete stack of articles has been assembled and pushed onto the outfeed conveyor, the pusher plate of the stack pusher assembly is retracted and the backstop of the back-up slide assembly is completely extended by operation of the single-acting back-up cylinder, such that the backstop can receive the first article of a new stack.
Therefore, it is an object of the invention to provide a stacker mechanism that can receive a plurality of single articles and assemble the articles into a side-by-side stack. It is an additional object of the invention to provide a stacker mechanism that supports the stack of articles while the stack is being assembled to prevent the stack from falling apart. It is another object of the invention to provide a stacker mechanism having a hold-back member that supports the innermost article of the stack and can be retracted to permit additional articles to be added to the stack. It is a further object of the invention to provide a method of assembling a stack of articles from a supply fed in a singulated fashion.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.